Breakable odor control additive for animal litter

ABSTRACT

A breakable odor control additive provides release of fragrance or odor masking scent when present in a litter formulation that is used by a cat or other animal within a litter box. The odor control additive comprises a plurality of fragrant-scented balls. Each of the balls has a central, compressible, porous, open-celled substrate, which is saturated with a fragrant scent. This central, fragrance-saturated substrate is coated with a barrier coating, which prevents evaporation of the fragrance and protects the substrate against deterioration by urine and other contaminants deposited on the litter. When cat or animal enters the litter box, a load is applied to the fragrant-scented balls. The barrier coating breaks, exposing the fragrant coated substrate. Fragrance evaporating from the substrate provides odor control and a pleasant scent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to additives for animal litter; and moreparticularly to an additive for cat litter, which releases an odorcontrolling or odor masking substance when the animal uses a litter-box.

2. Description of the Prior Art

Many patents disclose methods for control of odor in animal litter. Whenanimal litter is not of a clumping variety, it is difficult to controlthe odor since the urine excreted is absorbed over a much largerdistance. Clumps are created when the composition of the swells duringthe absorption of pet urine, creating a localized rigid clump. Typicaladditives for litter which provide this swelling and urine absorptionproperty include gypsum, calcium sulfate hemi-hydrate which absorbswater, forming CaSO₄.2H₂0, swelling Kaolin or montmorillonite clays.Gums of different variety are also used to dissolve and form a bond,creating clumps. Odor control is generally achieved by addingingredients to the litter that either mask the odor or add compoundsthat are anti-bacterial, or other compounds that exhibit pleasant smell.

U.S. Pat. No. 3,675,625 to Miller et al. teaches a litter which is“activated” by heating and then contacted with an odor control agent,such as pine oil, citrus oil, camphor or the like.

U.S. Pat. No. 4,203,388 to Cortigene et al. teaches the use of adeodorant such as sodium bicarbonate, in amounts of between about 1% andabout 10% of the dry weight of the litter. Such large amounts ofdeodorizer are necessitated since the litter itself is also used as anabsorbent for urine, requiring the deodorizer to be homogeneouslydispersed throughout the particles of the litter.

U.S. Pat. No. 4,405,354 to Thomas et al. discloses the use of bufferingagents to prevent gaseous ammonia from escaping into the air. However,such buffering agents serve only to prevent the formation of gaseousammonia; they are ineffective against other unpleasant odors. Further,the amounts of such agents range from about 0.5% to about 25% by weight,since all of the absorbent litter must be treated with the agent toprovide sufficient contact with the urine.

U.S. Pat. No. 4,459,368 to Jaffee, et al. discloses particulate sorbingand deodorizing mixtures containing synthetic and clay sorbents. Thecomposition contains sorbent fuller's earth clay particles and sorbentsynthetic particles, e.g. calcium sulfate dihydrate-containing granules,in a weight ratio of about 0.5:9.5 to about 4:6, respectively. Thiscombination of clay minerals and calcium sulfate dihydrate does notprovide odor control.

U.S. Pat. No. 4,517,919 to Benjamin et al. discloses the use ofundecylenic acid in amounts from about 1000 to about 10,000 ppm and abacteriostat in amounts from about 25 to 500 ppm. U.S. Pat. No.5,094,190 to Ratcliff et al. teaches an odor control animal litter towhich a boron-containing liquid material has been applied.

U.S. Pat. No. 5,097,799 discloses odor control agents selected from thegroup consisting of guanidine salts, alkali metal fluorides, alkalimetal bisulfites, and mixtures thereof. These agents are applied to thelitter using an aqueous dispersion to produce an odor control animallitter.

U.S. Pat. No. 5,183,655 teaches an odor control animal litter that hasapplied to it an effective amount of pine oil in combination with aneffective amount of boric acid.

U.S. Pat. No. 5,329,880 to Pattengill, et al. discloses clumpable animallitter. This waterproof litter contains a mixture of non-smectitic,hydrophilic shale aggregate with a fraction of coarse material with asize less than about 5 mesh (4000 microns). The mixture has the propertyof agglomerating into a clump upon contact with urine. The agglomeratedclump of shale and urine is removable with a perforated scoop. The shalemay contain up to 10 weight percent clumping agent selected from thegroup of water absorbent polymers, corn starch, gelatin, gluten anddried plants of the Plantago family. In addition 5 to 25 wt % ammoniaabsorbing zeolite may be added for odor control. The odor control agentis an absorbent for ammonia and does not provide odor control sinceammonia is not immediately formed.

U.S. Pat. No. 5,634,431 to Reddy, et al. discloses odor inhibiting petlitter. The addition of urease negative bacteria to sodium smectite clayminerals in pet litter inhibits growth of urease positive bacteria for aperiod of several days, thereby retarding formation of ammonia and otherobnoxious odors. Approximately fifty percent sodium bentonite in thelitter causes the litter to clump upon wetting, maintaining the urea incontact with the treated clay and also serving as a buffer to favorgrowth of the urease negative bacteria. This composition entirely relieson inhibiting ammonia formation and does not provide immediately apleasant scent.

U.S. Pat. No. 5,806,462 to Parr discloses clumping animal litter. Theanimal litter, is particularly for cats and has a gelatin solution and adry adhesive sprayed onto the granules. The gelatin solution providesenough dampening to adhere the adhesive particles to the clay particles.Because the gelatin sets quickly, it does not provide so much wetting asto activate the adhesive. Therefore, the adhesive retains its adhesiveproperties and, together with the gelatin, causes the litter to clumpwhen wetted by an animal. This clumping cat litter formulation providesno odor control.

U.S. Pat. No. 5,975,019 to Goss, et al. discloses clumping animallitter. The clumping animal litter utilizes the interparticleinteraction of a sodium bentonite swelling clay with a non-swelling claymaterial. Preferably, sixty percent (60%) by weight, or less,composition of sodium bentonite is used after the judicious selection ofparticle size distribution such that the mean particle size of thenon-swelling clay material is greater than the mean particle size of thesodium bentonite. In addition, an organic clumping agent, such as apregelatinized corn starch can be combined with the sodiumbentonite/clay mixture to enhance clumping properties. This clumpingclay litter does not control odor.

U.S. Pat. No. 5,992,351 to Jenkins discloses clumpable animal litterwith improved odor control. The clumpable animal litter with improvedodor control comprises a) water-swellable clay particles capable ofadhering other such particles upon contact with moisture; and b) an odorcontrolling-effective amount of a boron compound of a compositiondi-alkali metal tetraborate n-hydrate, wherein n is 4, 5 or 10, whichcontrols odors arising from the contact of said clay particles withmoisture.

U.S. Pat. No. 6,206,947 to Evans, et al. discloses a process for makingan animal litter comprising gypsum, aluminum sulfate and urea. Theanimal litter composition is an agglomerated or compacted calcinedcalcium sulfate absorbent. The animal litter composition is screened toa particle size between 6 mesh and about 100 mesh and an effectiveamount of a binder such as a clay, lignin or starch is added to thecalcium sulfate to assist the calcium sulfate to pelletize. This is agypsum composition that is agglomerated using aluminum sulfate and ureato chemically combine with gypsum. There is no odor control in thisclumping litter composition.

U.S. Pat. No. 6,253,710 to Ward, et al. discloses odor control foranimal litter. It uses an odor control liquid and an aerosolizedcomposition for deodorizing and controlling the odor of animal wastes.The liquid and aerosolized composition comprises a non-aqueous volatilecarrier and an odor control agent. The liquid and aerosolizedcomposition can be applied in liquid form directly to the animal litterand/or the animal container and/or the animal waste. The littercontainer may be sprayed with a powdered release agent which may betalc, of talc, inorganic silicone and magnesium powders, sodiumbicarbonate, chlorophyll, sodium dihydrogen phosphate, potassium acidphthalates, or their mixtures preventing the stickiness of the odorcontrolling liquid. The liquid mixes with the litter product and alwaysevaporating disseminates the odor control agent and is quicklyexhausted.

There remains a need in the art for a cat or animal litter compositioncontaining ingredients that release a pleasant scent after the cat oranimal uses the litter, eliminating the malaise odor of common litterboxes.

SUMMARY OF THE INVENTION

The present invention provides a litter formulation for a cat or animallitter having fragrance-scented balls that comprise an open-celled,porous compressible substrate. The substrate is saturated with fragrantscent and covered with a barrier layer that substantially preventsevaporation of the fragrant scent and absorption of urine and animalexcrement. When a cat or an animal enters a litter box containing thefragrance-scented balls mixed with litter, the force exerted by the cator animal's body breaks the shell of the barrier layer. Fracture of thebarrier layer exposes the compressible porous substrate, triggeringrelease of the impregnated fragrance. This fragrance is delivered atsubstantially the same time as the cat or the animal disturbs the litterin the litter box, creating an environment free from unpleasant odor.

Generally stated, the fragrance-scented balls have a central core ofspongy, open-celled, compressible, porous substrate that has sufficientvolumetric porosity to saturate and retain impregnated scent. As usedherein, the term “balls” is intended to mean spherical, cylindrical,cubical and other irregular geometric shapes. Preferably, the poroussubstrate is a foam made from a polymeric material such as polyurethane.The scent may be impregnated in the form of an aqueous or non-aqueouscarrier, wherein the fragrance composition is dissolved. Alternatively,the pores of the compressible substrate comprise an impregnated, solidfragrance that has a fragrance vapor pressure greater than oneatmosphere so that, when exposed to air, the fragrance is released as avapor. In order to prevent the fragrance from constantly being releasedfrom the fragrant-scented balls, the surface of the fragrant-scentedballs is provided with a barrier coating. The barrier coatingessentially traps the liquid or fragrance vapor and prevents exhaustionof the fragrant scent. Release of the fragrance is activated only whenthe barrier layer is broken, for example, by the weight of a cat oranimal using the litter box. The barrier coating also prevents thecompressible porous substrate from soaking in urine or animal excrement,so that the fragrant-scented balls remain saturated with the fragranceuntil such a time that the barrier coating is actually broken.

In a preferred embodiment, the litter used is of a clumping variety,thereby minimizing the extent of spread of urine in a liter box. Thearea near the clumped region is disturbed by the animal and this isprecisely the area in which the scented fragrance is released. Theoverall litter in the litter box is generally undisturbed and thefragrant-scented balls continue to retain the fragrance, since thebarrier coatings thereof are not broken.

The barrier coating is applied after the porous compressible substrateis soaked with fragrant scent. The scent may be a fragrance dissolved inan aqueous, non-aqueous carrier or dispersion of solid powder with asolid fragrance powder having a fragrance vapor pressure greater thanone atmosphere. In the case of liquid compositions, the fragrance isdissolved in water, or a suitable organic solvent such as acetone,isopropyl alcohol and the like, and is saturated in the poroussubstrate. The barrier coating is then applied to the fragrancesaturated, compressible porous substrate. The requirements for the thinbarrier coating are: 1) the barrier coating should prevent theevaporation of the fragrance; 2) the barrier coating should shield thefragrant-scented ball, and prevent its interior from becoming soaked inthe urine and animal excrement; and 3) the barrier coating should breakunder load when a cat or other animal steps into the litter box. Manybarrier coatings fill this need. A number of polymeric coatings providethis functionality. Since the applied barrier coating is generally thin,having a coating thickness of 75 to 250 microns, and is placed over acompressible substrate, it breaks easily under load, thereby releasingthe fragrance saturated in the porous substrate. The barrier coating mayinclude thermoplastic polymers dissolved in a solvent and applied as athick syrupy solution. Evaporation of the solvent causes formation ofthe barrier coating. An example of polymer dissolved in a solvent ispolymethyl methacarylate (PMMA) dissolved in dichloromethane. Thebarrier coating may be a condensation thermosetting system wherein thepolymer is coated first, followed by a cross-linking agent. One exampleof this system is a resinous composition produced by mixing an aromaticprimary amine with an aqueous emulsion containing a polymer ofacrylamide and formaldehyde, as disclosed in U.S. Pat. No. 4,107,119 toKameyama, et al. Another method of forming the barrier coating comprisesthe steps of dipping the fragrant scent-saturated porous compressiblesubstrate in molten wax, and allowing the wax to solidify. Waxes usedfor forming a barrier coating may include whale wax, beeswax, paraffinwax and higher fatty acids such as myristic, plamitic, stearic andbehenic acids, and esters thereof. Another barrier coating methodcomprises the steps of coating the fragrant scent-saturated porouscompressible substrate with a mixture of gypsum in water and hardeningthe gypsum coating by hydration. This method results in a ceramic likeshell, which readily cracks when a cat or other animal enters the litterbox.

The odor control agent in the fragrant scent balls may be laurylmethacrylate (sold under trade name METAZENE by Pestco Company),dissolved in acetone, a non-aqueous volatile carrier. Fragrance used tosaturate the substrate may include natural fragrance extracted fromplant materials, fragrances chemically synthesized to imitate naturalfragrances or synthetic fragrances.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood and further advantages willbecome apparent when reference is had to the following detaileddescription of the preferred embodiments of the invention and theaccompanying drawing, in which:

FIG. 1 is a schematic diagram showing a fragrant-scented ball comprisinga porous compressible fragrance saturated substrate coated with abarrier layer; and

FIG. 2 is a diagrammatic representation of the process of manufacturinga fragrant-scented ball for use in a litter box as an additive.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to an additive for litters used by cats and otheranimals. The additive releases an odor neutralizing, pleasant fragrancewhen the litter is used by a cat or animal. Generally stated, theadditive is a fragrant-scented ball, which may be added to the litteror, alternatively, may be packaged with litter. The fragrant-scentedball includes a fragrance saturated open-celled porous compressiblesubstrate, which is coated with a barrier layer that breaks under theweight of the cat or animal when a litter box is used. The term ballincludes spherically shaped substrates, cylindrically shaped substratesor cube shaped substrates or other regular or irregularly shapedsubstrates. The barrier layer prevents the evaporation of the fragrance.It releases the fragrance only when the barrier coating is broken by theweight of a cat or other animal that uses the cat litter. The barriercoating also protects the fragrance saturated porous substrate frombeing saturated with cat or animal urine and excrements. Preferably, thefragrant-scented ball additive is used in conjunction with a clumpinglitter, which reduces or minimizes the spreading of urine due to theclumping action. The clumping litter generally uses a mixture ofswelling clay composition together with non-swelling clay composition asdiscussed in U.S. Pat. No. 5,975,019 to Goss, et al. or mixture ofgypsum with clay as discussed in U.S. Pat. No. 4,459,368 to Gaffe et al.

Generally stated, the invention involves the use of fragrant-scentedballs, which have a fragrance saturated, open-celled, porouscompressible substrate. Such substrate is completely covered with abarrier coating that prevents the evaporation of the fragrance saturatedwithin the substrate. The fragrance may be an odor neutralizing ormasking compound or a pleasant smelling fragrance. A typical odorneutralizing or masking compound is lauryl methacrylate (sold undertrade name METAZENE by Pestco Company). The masking compound isdissolved in acetone, a non-aqueous volatile carrier. Representativeexamples of fragrance components generally include, but are not limitedto: volatile phenolic substances (such as iso-amyl salicylate, benzylsalicylate, and thyme oil red); essence oils (such as geranium oil,patchouli oil, and petitgrain oil); citrus oils; extracts and resins(such as benzoin siam resinold and opoponax resinold); “synthetic” oilssuch as Bergamot 37 and 430, Geranium 76 and Pomeransol 314, and PowderMask CE-32907); aldehydes and ketones (such as beta-methyl naphthylketone, p-tert-butyl-a-methyl hydrocinnamic aldehyde and p-tert-amylcyclohexanone); polycyclic compounds (such as Coumarin and beta-naphthylmethyl ether); esters (such as diethyl phthalate, phenylethylphenylacetate). Fragrances also include esters and essential oilsderived from floral materials and fruits, citrus oils, absolutes,aldehydes, etc. and alcohols (such as dimyrcetol, phenylethyl alcoholand tetrahydromuguol). Generally the fragrances are dissolved in aqueousor non-aqueous carrier and the fragrance soaked substrate is coated witha barrier layer, which prevents the evaporation of the carrier and thefragrance. Alternatively, the fragrance may be in the form of a solidpowder wherein the vapor pressure of the fragrance is greater than oneatmosphere thereby disseminating the fragrance when the barrier coatingis broken.

The barrier layer has several key requirements. It must prevent theevaporation of the fragrance entrained within the open-celled poroussubstrate. When a liquid fragrance is used together with a carrier, thebarrier should be resistant to the carrier, which may be aqueous ornon-aqueous. Secondly, the barrier coating must be water insoluble andresist urine and cat or animal excrements from contaminating thefragrance saturated in the substrate. Thirdly, the barrier coating mustbe sufficiently thin that it breaks when a cat or other animal walksover the litter in the litter box. Since the substrate is porous andcompressible, it provides very limited support to the barrier coating.Typically, the barrier coating is 75 to 250 microns thick, and thesubstrate has a linear dimension of 1000 microns to 5000 microns. Thesubstrate is produced from open cell foam of polyurethane or rubber orother suitable polymeric material. Smaller diameter of substrate incombination with a thicker barrier coating provides fragrant-scentedballs, which survive packaging when mixed in litterbags and still breakunder load of a cat or animal in a litter box. Larger diametersubstrates with thinner barrier coatings provide fragrant-scented ballssuitable for individual packaging, which is added by the user to alitter box.

The barrier coating may be applied in one of several methods. In thefirst method, the barrier coating is a thermoplastic polymer layer. Thethermoplastic polymer is dissolved in a solvent to form a thick syrupyliquid. The fragrance saturated, open-celled porous compressiblesubstrate is dipped in the syrupy polymeric liquid and the solvent isevaporated to fashion the barrier coating. One example of polymerdissolved in a solvent is polymethyl methacarylate (PMMA) dissolved indichloromethane or other suitable solvent. This operation is carried outin a rotating drum or barrel so that the syrupy polymeric liquid coatseach substrate and the solvent evaporates, keeping the barrier coatedsubstrates apart from one another. In a second method, the fragrancesaturated open-celled porous compressible substrate is coated with athermosetting resin and a cross-linking agent. This operation is alsoprocessed in a rotating drum or barrel wherein the resin andcross-linking agent are added sequentially. The product is removed afterthe barrier coating is formed. An example of a cross-linking coatingsystem uses aromatic primary amine with acrtylamide polymer andformaldehyde. In a third barrier coating method, the fragrance saturatedopen-celled porous compressible substrate is sprayed with or dipped inmolten wax composition. This operation is also processed in a rotatingdrum or barrel. The hot molten wax coats the saturated substrate andfreezes, forming a barrier coating. The rotation of the drum or barrelprevents the barrier-coated substrates from sticking to each other. In afourth method, the fragrance-saturated, open-celled, porous compressiblesubstrate is coated with a gypsum-water mixture. Gypsum is calciumsulfate hemihydrate, and chemically combines with water to set gypsumforming crystals of calcium sulfate dihydrate. Again, this operation iscarried out in a rotating drum or barrel.

The following examples are provided to more completely describe theproperties of the present invention. The specific techniques,conditions, materials, proportions and reported data set forth toillustrate the principles and practice of the invention are exemplaryonly and should not be construed as limiting the scope of the invention.

EXAMPLE 1

Cellulose acetate open cell foam is cut to 1500 micron cubes and issaturated with Listerine mouth wash, the fragrance of which is easilyrecognized. A gypsum water mixture is constituted by thoroughly mixing 8oz of water to one pound of gypsum. The Listerine saturated substrate isimmersed in the gypsum water mix and is withdrawn, resulting in auniform barrier coating. The barrier coating hardens within 20 minutes.The barrier-coated substrate is broken to release the saturatedListerine fragrance.

Cellulose acetate open cell foam is cut to 1500 micron cubes and issaturated with Listerine mouth wash, the fragrance of which is easilyrecognized. Paraffin wax is melted in a metallic container. Upon beingmeasured, the melting point is determined to be 55° C., and the melt isheated to 65° C. The Listerine saturated substrate is dipped in hot waxmelt and then withdrawn. The adherent wax melt layer solidifies within 3minutes, forming the barrier coating. The barrier-coated substrate isbroken to release the saturated Listerine fragrance.

FIG. 1 is a schematic diagram showing a fragrant-scented ball 10 havinga central fragrance saturated porous compressible substrate 11 coatedwith a barrier layer 12. The central porous compressible substrate isopen cell foam fabricated from polyurethane, or latex rubber or othersuitable polymeric materials. The open cell pores 13 provide spaceswithin which the fragrance scent is incorporated. The fragrant scent maybe carried in an aqueous or non-aqueous carrier or may be in the form ofa powder dispersed within the open cell structure of the foam. Theporous compressible substrate has a linear dimension in the range of1000 to 5000 microns, and the barrier coating is in the range of 75 to250 microns. The barrier layer is selected to prevent the evaporation ofthe fragrance saturated in the porous substrate. It breaks under loadwhen a cat or animal uses a litter box containing fragrant-scentedballs, and resists deterioration by urine and other animal excrement.

Referring to FIG. 2, there is shown generally at 20 a diagrammaticrepresentation of the process of manufacturing a fragrant-scented ball.In step 1, the porous compressible substrate is prepared. In step 2, theporous compressible substrate is saturated with a fragrant scent. Thismay be accomplished by a liquid immersion process (not shown) or use ofa spray process, as shown, that soaks the porous compressiblesubstrates. In step 3, the fragrance saturated porous compressiblesubstrates are transferred to a rotating drum or barrel. The barriercoating is applied in the form of spray, as shown, or by other means inthe rotating drum to coat each substrate with the barrier layer and keepindividual substrates apart so that they do not stick to each other.

Significant advantages are realized by practice of the presentinvention. The key components of the breakable odor control additive foranimal litter include, in combination, the features set forth below;

-   -   1. a breakable odor control additive for animal litter        comprising a plurality of fragrant-scented balls;    -   2. each fragrant-scented ball having a central porous        compressible substrate saturated with a fragrant scent and        coated with a barrier layer;    -   3. the central fragrance-saturated, porous compressible        substrate providing very limited support to the barrier layer;    -   4. the barrier layer braking under load of a cat or animal using        a litter box containing the litter and fragrant-scented balls,        triggering release of the fragrance;    -   5. the barrier layer substantially preventing evaporation of the        saturated fragrance in the porous compressible substrate until        broken;    -   6. The barrier layer substantially preventing the degradation of        fragrance saturated in the porous compressible substrate due to        urine and cat or animal excrements.

The process of manufacturing a fragrant-scented ball includes the stepsset forth below:

-   -   1. selecting open-celled, foam material having appropriate        shape, size and compressibility for substrates;    -   2. saturating porous compressible substrates with a liquid        fragrance in a carrier or incorporating solid fragrance within        open cells of the porous compressible substrate;    -   3. coating the fragrance-saturated, porous, compressible,        open-cell substrate with a compound that hardens to form a        barrier layer;    -   4. packaging the fragrant-scented balls as an additive for        litter or mixing them with a litter formulation that is packaged        for sale.

Having thus described the invention in rather full detail, it will beunderstood that such detail need not be strictly adhered to, but thatadditional changes and modifications may suggest themselves to oneskilled in the art, all falling within the scope of the invention asdefined by the subjoined claims.

1. An odor control additive for litter, comprising: a. a plurality offragrant-scented balls adapted to be added to litter; b. saidfragrant-scented balls comprising a central, open-celled, porouscompressible substrate and a barrier coating covering said substrate; c.said central, porous compressible substrate being saturated with afragrance; d. said barrier coating being supported by said centralporous compressible substrate; e. said barrier coating resistingfragrance degradation by urine and cat or animal excrements, wherebysaid fragrant-scented balls within said litter are operative to breakunder load in response to the weight of a cat or other animal using saidlitter box, thereby releasing fragrance saturated in the central porouscompressible substrate.
 2. The odor control additive as recited by claim1, wherein said central open-celled porous compressible substrate is apolyurethane open-cell foam.
 3. The odor control additive as recited byclaim 1, wherein said central open-celled porous compressible substrateis a latex rubber open-cell foam.
 4. The odor control additive asrecited by claim 1, wherein said fragrance is an odor controlling orodor masking compound.
 5. The odor control additive as recited by claim4, wherein said odor controlling or odor masking compound is laurylmethacrylate.
 6. The odor control additive as recited by claim 1,wherein said fragrance is a natural plant-base fragrance.
 7. The odorcontrol additive as recited by claim 1, wherein said fragrance is asynthetic fragrance replicating a natural fragrance.
 8. The odor controladditive as recited by claim 1, wherein said barrier coating is athermoplastic resin.
 9. The odor control additive as recited by claim 1,wherein said barrier coating is a thermosetting resin.
 10. The odorcontrol additive as recited by claim 1, wherein said barrier coating isa wax composition.
 11. The odor control additive as recited by claim 1,wherein said barrier coating is a gypsum composition.
 12. The odorcontrol additive as recited by claim 1, wherein said central open-celledporous compressible substrate has a linear dimension of about 1000 to5000 microns.
 13. The odor control additive as recited by claim 1,wherein said barrier coating has a thickness of about 75 to 250 microns.14. A process for manufacturing an odor control additive for a litterformulation, comprising the steps of; a. selecting open-celled foammaterial having appropriate shape, size and compressibility forsubstrates; b. saturating porous compressible substrates with a liquidfragrance in a carrier disposed within open cells of the porouscompressible substrate; c. coating the fragrance saturated porouscompressible open-cell substrate with a barrier layer; and d. addingsaid fragrant-scented balls to said litter formulation.
 15. A processfor manufacturing an odor control additive for a litter formulation,comprising the steps of; a. selecting open-celled foam material ofappropriate shape, size and compressibility for substrates; b.saturating porous compressible substrates with a fragrance toincorporate said fragrance within open cells of the porous compressiblesubstrate; c. coating the fragrance saturated porous compressible opencell substrate with a barrier layer; d. packaging the fragrant-scentedballs as an additive for said litter formulation.